This year the Section on Structural Chemistry has been involved in several projects. Most of these relate to the analysis of peptides and proteins, but there are several others as well: 1. We are attempting to elucidate the structure of a substance which inhibits growth of the malaria organism in the mosquito. We have determined its mass, formula and several properties, all on nanogram amounts. It appears to be a peptide-like structure with at least 3 basic nitrogens, however it does not show mass spectral fragmentation typical of peptides. A tentative structure has been proposed. With R. Miller, S. Cociancick and M. Shahabuddin, NIAD 2. Peptidyl glycine hydroxylating monooxygenase (PHM) is an enzyme responsible for converting C-terminal glycine to the C-terminal amide function in proteins and controls formation of certain neuropeptides. It is irreversibly inhibited by styrylacetic acid forming two compounds in the process. We have identified one of these as the 2-hydroxy derivative and the second as an isomer of it. This should shed light on the mechanism by which this protein hydroxylates the glycine residue. With G. Mueller and W. Driscoll USUHS. 3. In the area of mass spectral techniques, we have discovered that a simple liquid junction designed by us provides much improved spectra, especially in the negative ion mode. This arrangement was used to prove that a much more complex device accompanied by an explanation invoking a "cylindrical capacitor interface" (published by another group) was unnecessarily complex. 4. Several proteins derived from PAGE gels at the 1-2 picomole level have been degraded by trypsin and their peptides detected . These include the PHM enzyme discussed above and a chemokine receptor. With B. Chock, NHLBI. 5. Accurate mass measurement is available up to m/z 10,000 on one of our newer spectrometers so that calibration is now critical. We have found that a series of cesium salts of perfluoroalkyl acids are suitable for this purpose since they provide high mass salt/acid oligimer adducts. 6. A second method has been devised for rapidly desalting (on-line)proteins prior to analysis by the electrospray technique. This works well at the 1-5 ul range and is used frequently for this purpose. It has allowed analysis of the oxidation sites of cysteine residues in a recombinant protein-tyrosine phosphatase. In related work glutathionylation of the PT1B protein was determined by mass spectrometry and is suggested as a reversible control of the protein's activity. With B. Barrett and B. Chock, NHLBI. 7. A series of N-nitrosated N-hydroxyguanidines used as models for the formation of NO in vivo has been examined with the very mild electrospray process in an effort to avoid loss of the NO moiety, and their fragmentation patterns reported. 8. Aldose reductase from pig,rat and human have been studied by MS and found to form binary and tertiary complexes with NADPH and various inhibitors. these are being studied as models for isolating the natural human endogenous inhibitor. With P. Kador, NEI. 9. Phosphorylation of the amino terminal domain of Enzyme 1 promotes transfer of phosphate to the phosphocarrier protein Hpr and this was demonstrated by mass spectral analysis. With Ann Ginsburg, NHLBI.